Charge transport compositions and electronic devices made with such compositions

ABSTRACT

The present invention relates to charge transport compositions. The invention further relates to electronic devices in which there is at least one active layer comprising such charge transport compositions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 10/612,704,filed Jul. 10, 2003, now allowed, which claims priority from U.S.Provisional Application Ser. No. 60/394,767, filed Jul. 10, 2002, andU.S. Provisional Application Ser. No. 60/458,277, filed Mar. 28, 2003,both of which are incorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to charge transport compositions. Theinvention further relates to photoactive electronic devices in whichthere is at least one active layer comprising such charge transportcompositions.

2. Background

In organic photoactive electronic devices, such as light-emitting diodes(“OLED”), that make up OLED displays, the organic active layer issandwiched between two electrical contact layers in an OLED display. Inan OLED the organic photoactive layer emits light through thelight-transmitting electrical contact layer upon application of avoltage across the electrical contact layers.

It is well known to use organic electroluminescent compounds as theactive component in light-emitting diodes. Simple organic molecules,conjugated polymers, and organometallic complexes have been used.

Devices which use photoactive materials, frequently include one or morecharge transport layers, which are positioned between the photoactive(e.g., light-emitting layer) layer and one of the contact layers. A holetransport layer may be positioned between the photoactive layer and thehole-injecting contact layer, also called the anode. An electrontransport layer may be positioned between the photoactive layer, such asthe organometallic light emitting material, in photoactive devices, andthe electron-injecting contact layer, also called the cathode.

There is a continuing need for charge transport materials andanti-quenching materials.

SUMMARY OF THE INVENTION

The present invention is directed to a charge transport compositionwhich is a quinoxaline derivative. The quinoxaline derivative hasFormula I, shown in FIG. 1, wherein:

-   -   R¹ and R² are the same or different at each occurrence and are        selected from H, F, Cl, Br, hydroxyl, carboxyl, carbonyl, silyl,        siloxyl, alkyl, heteroalkyl, alkenyl, alkynyl, aryl, heteroaryl,        alkylenearyl, alkenylaryl, alkynylaryl, alkyleneheteroaryl,        alkenylheteroaryl, alkynylheteroaryl, C_(n)H_(a)F_(b),        OC_(n)H_(a)F_(b), C₆H_(c)F_(d), and OC₆H_(c)F_(d), or both of R²        together may constitute an arylene or heteroarylene group;    -   a, b, c, and d are 0 or an integer such that a+b=2n+1, and        c+d=5,    -   n is an integer from 1 through 12; and    -   z is 0 or an integer from 1 through 4.

In another embodiment, the present invention is directed to a chargetransport composition having Formula II, shown in FIG. 2, wherein:

-   -   R¹, R², a through d and n are as defined above,    -   R³ is the same or different at each occurrence and is selected        from a single bond and a group selected from alkylene,        heteroalkylene, arylene, heteroarylene, arylenealkylene, and        heteroarylenealkylene; alkynylene, alkynylenearylene,        alkynyleneheteroarylene.    -   Q is selected from a single bond and a multivalent group;    -   m is an integer equal to at least 2,    -   p is 0 or 1 and    -   x is 0 or an integer from 1 to 3.

In another embodiment, the present invention is directed to a chargetransport composition having Formula III, shown in FIG. 3, wherein:

-   -   R¹, R², a through d, n, and z are as defined above,    -   R³ is the same or different at each occurrence and is selected        from a single bond and a group selected from alkylene,        heteroalkylene, arylene, heteroarylene, arylenealkylene, and        heteroarylenealkylene; alkynylene, alkynylenearylene,        alkynyleneheteroarylene.    -   Q is selected from a single bond and a multivalent group;    -   m is an integer equal to at least 2; and    -   p is 0 or 1.

In another embodiment, the present invention is directed to anelectronic device having at least one active layer comprising a materialselected from Formulae I, II, and III, shown in FIGS. 1 through 3,wherein Ar¹, R¹ through R³, Q, a through d, m, n, p, x, and z are asdefined above.

As used herein, the term “charge transport composition” is intended tomean material that can receive a charge from an electrode andfacilitates movement through the thickness of the material withrelatively high efficiency and small loss of charge. Hole transportcompositions are capable of receiving a positive charge from an anodeand transporting it. Electron transport compositions are capable ofreceiving a negative charge from a cathode and transporting it. The term“anti-quenching composition” is intended to mean a material whichprevents, retards, or diminishes both the transfer of energy and thetransfer of an electron to or from the excited state of the photoactivelayer to an adjacent layer. The term “photoactive” refers to anymaterial that exhibits electroluminescence, photoluminescence, and/orphotosensitivity. The term “HOMO” refers to the highest occupiedmolecular orbital of a compound. The term “LUMO” refers to the lowestunoccupied molecular orbital of a compound. The term “group” is intendedto mean a part of a compound, such as a substituent in an organiccompound. The prefix “hetero” indicates that one or more carbon atomshas been replaced with a different atom. The term “alkyl” is intended tomean a group derived from an aliphatic hydrocarbon having one point ofattachment, which group may be unsubstituted or substituted. The term“heteroalkyl” is intended to mean a group derived from an aliphatichydrocarbon having at least one heteroatom and having one point ofattachment, which group may be unsubstituted or substituted. The term“alkylene” is intended to mean a group derived from an aliphatichydrocarbon and having two or more points of attachment. The term“heteroalkylene” is intended to mean a group derived from an aliphatichydrocarbon having at least one heteroatom and having two or more pointsof attachment. The term “alkenyl” is intended to mean a group derivedfrom a hydrocarbon having one or more carbon-carbon double bonds andhaving one point of attachment, which group may be unsubstituted orsubstituted. The term “alkynyl” is intended to mean a group derived froma hydrocarbon having one or more carbon-carbon triple bonds and havingone point of attachment, which group may be unsubstituted orsubstituted. The term “alkenylene” is intended to mean a group derivedfrom a hydrocarbon having one or more carbon-carbon double bonds andhaving two or more points of attachment, which group may beunsubstituted or substituted. The term “alkynylene” is intended to meana group derived from a hydrocarbon having one or more carbon-carbontriple bonds and having two or more points of attachment, which groupmay be unsubstituted or substituted. The terms “heteroalkenyl”,“heteroalkenylene”, “heteroalkynyl” and “heteroalkynlene” are intendedto mean analogous groups having one or more heteroatoms. The term “aryl”is intended to mean a group derived from an aromatic hydrocarbon havingone point of attachment, which group may be unsubstituted orsubstituted. The term “heteroaryl” is intended to mean a group derivedfrom an aromatic group having at least one heteroatom and having onepoint of attachment, which group may be unsubstituted or substituted.The term “arylalkylene” is intended to mean a group derived from analkyl group having an aryl substituent, which group may be furtherunsubstituted or substituted. The term “heteroarylalkylene” is intendedto mean a group derived from an alkyl group having a heteroarylsubstituent, which group may be further unsubstituted or substituted.The term “arylene” is intended to mean a group derived from an aromatichydrocarbon having two points of attachment, which group may beunsubstituted or substituted. The term “heteroarylene” is intended tomean a group derived from an aromatic group having at least oneheteroatom and having two points of attachment, which group may beunsubstituted or substituted. The term “arylenealkylene” is intended tomean a group having both aryl and alkyl groups and having one point ofattachment on an aryl group and one point of attachment on an alkylgroup. The term “heteroarylenealkylene” is intended to mean a grouphaving both aryl and alkyl groups and having one point of attachment onan aryl group and one point of attachment on an alkyl group, and inwhich there is at least one heteroatom. Unless otherwise indicated, allgroups can be unsubstituted or substituted. The phrase “adjacent to,”when used to refer to layers in a device, does not necessarily mean thatone layer is immediately next to another layer. On the other hand, thephrase “adjacent R groups,” is used to refer to R groups that are nextto each other in a chemical formula (i.e., R groups that are on atomsjoined by a bond). The term “compound” is intended to mean anelectrically uncharged substance made up of molecules that furtherconsist of atoms, wherein the atoms cannot be separated by physicalmeans. The term “ligand” is intended to mean a molecule, ion, or atomthat is attached to the coordination sphere of a metallic ion. The term“complex”, when used as a noun, is intended to mean a compound having atleast one metallic ion and at least one ligand. The term “polymeric” isintended to encompass oligomeric species and include materials having 2or more monomeric units. In addition, the IUPAC numbering system is usedthroughout, where the groups from the Periodic Table are numbered fromleft to right as 1 through 18 (CRC Handbook of Chemistry and Physics,81^(st) Edition, 2000).

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Unless otherwise defined, allletter symbols in the figures represent atoms with that atomicabbreviation. Although methods and materials similar or equivalent tothose described herein can be used in the practice or testing of thepresent invention, suitable methods and materials are described below.All publications, patent applications, patents, and other referencesmentioned herein are incorporated by reference in their entirety. Incase of conflict, the present specification, including definitions, willcontrol. In addition, the materials, methods, and examples areillustrative only and not intended to be limiting.

Other features and advantages of the invention will be apparent from thefollowing detailed description, and from the claims.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows Formula I for a charge transport composition of theinvention.

FIG. 2 shows Formula II for a charge transport composition of theinvention.

FIG. 3 shows Formula III for a charge transport composition of theinvention.

FIG. 4 shows Formulae I(a) through I(ag) for a charge transportcomposition of the invention.

FIG. 5 shows Formulae IV(a) through IV(h) for a multidentate linkinggroup.

FIG. 6 shows Formulae II(a) through II(l) for a charge transportcomposition of the invention.

FIG. 7 shows Formulae V(a) through V(e) for electroluminescent iridiumcomplexes.

FIG. 8 is a schematic diagram of a light-emitting diode (LED).

FIG. 9 is a schematic diagram of a testing device for an LED.

FIG. 10 shows formulae for known electron transport compositions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The quinoxaline derivative compounds represented by Formula I, shown inFIG. 1, have particular utility as electron transport compositions andas anti-quenching agents. The quinoxaline compounds can also be used ashosts for light emitting materials.

In general, n is an integer. In one embodiment, n is an integer from 1through 20. In one embodiment, n is an integer from 1 through 12.

In one embodiment, R¹ is selected from phenylalkenyl and phenylakynylgroups, which may be further substituted.

In one embodiment, R¹ is selected from alkylacetate and arylcarbonylgroups, which may be further substituted.

In one embodiment, R¹ is selected from alkyl groups having 1 through 12carbon atoms.

In one embodiment, R² is selected from phenyl groups, substituted phenylgroups, pyridyl groups, and substituted pyridyl groups. The substituentcan be selected from F, Cl, Br, hydroxyl, carboxyl, carbonyl, silyl,siloxyl, alkyl, heteroalkyl, alkenyl, alkynyl, aryl, heteroaryl,alkylenearyl, alkenylaryl, alkynylaryl, alkyleneheteroaryl,alkenylheteroaryl, alkynylheteroaryl, C_(n)H_(a)F_(b), OC_(n)H_(a)F_(b),C₆H_(c)F_(d), and OC₆H_(c)F_(d).

In one embodiment, both of R² together are a biarylene group, which maybe further substituted. In one embodiment, the biarylene group isselected from biphenylene and bipyridylene. The substituent can beselected from F, Cl, Br, hydroxyl, carboxyl, cabonyl, silyl, siloxyl,alkyl, heteroalkyl, alkenyl, alkynyl, aryl, heteroaryl, alkylenearyl,alkenylaryl, alkynylaryl, alkyleneheteroaryl, alkenylheteroaryl,alkynylheteroaryl, C_(n)H_(a)F_(b), OC_(n)H_(a)F_(b), C₆H_(c)F_(d), andOC₆H_(c)F_(d).

Examples of suitable ET/AQ compounds of this type include, but are notlimited to those given as Formulae I(a) through I(ag) in FIG. 4.

The compositions represented by Formula I can be prepared using standardsynthetic organic techniques, as illustrated in the examples. Thecompounds can be applied as thin films by evaporative techniques orconventional solution processing methods. As used herein, “solutionprocessing” refers to the formation of films from a liquid medium. Theliquid medium can be in the form of a solution, a dispersion, anemulsion, or other forms. Typical solution processing techniquesinclude, for example, solution casting, drop casting, curtain casting,spin-coating, screen printing, inkjet printing, gravure printing, andthe like.

In some cases it is desirable to increase the Tg of the compounds toimprove stability, coatability, and other properties. This can beaccomplished by linking together two or more of the compounds with alinking group to form compounds having Formula II, shown in FIG. 2, orFormula III, shown in FIG. 3. In these formulae, Q can be a single bondor a multivalent linking group, having two or more points of attachment.The multivalent linking group can be a hydrocarbon group with two ormore points of attachment, and can be aliphatic or aromatic. Themultivalent linking group can be a heteroalkylene or heteroarylenegroup, where the heteroatoms can be, for example, N, O, S, or Si.Examples of multivalent groups, Q, include, but are not limited to,alkylene, alkenylene, and alkynylene groups, and analogous compoundswith heteroatoms; single, multiple-ring, and fused-ring aromatics andheteroaromatics; arylamines, such as triarylamines; silanes andsiloxanes. Additional examples of multivalent Q groups are given in FIG.5 as Formulae IV(a) through IV(h). In Formula IV(f), any of the carbonsmay be linked to a charge transport moiety. In Formula IV(h), any of theSi atoms can be linked to a charge transport moiety. Heteroatoms such asGe and Sn can also be used. The linking group can also be—[SiMeR¹—SiMeR¹]_(n)—, where R¹ and n are as defined above.

In general, m is an integer equal to at least 2. The exact numberdepends on the number of available linking positions on Q and on thegeometries of the quinoxaline moiety and Q. In one embodiment, m is aninteger from 2 through 10.

In one embodiment, in Formula II, R¹ is selected from phenyl andsubstituted phenyl groups. The substituents can be selected from F, Cl,Br, alkyl, heteroalkyl, alkenyl, and alkynyl.

In one embodiment, in Formula II, R¹ is selected from alkylacetate andarylcarbonyl groups, which may be further substituted.

In one embodiment, in Formula II, R¹ is selected from alkyl groupshaving 1 through 12 carbon atoms.

In one embodiment, in Formula II, R² is selected from phenyl groups,substituted phenyl groups, pyridyl groups, and substituted pyridylgroups. The substituent can be selected from F, Cl, Br, hydroxyl,carboxyl, carbonyl, silyl, siloxyl, alkyl, heteroalkyl, alkenyl,alkynyl, aryl, heteroaryl, alkylenearyl, alkenylaryl, alkynylaryl,alkyleneheteroaryl, alkenylheteroaryl, alkynylheteroaryl,C_(n)H_(a)F_(b), OC_(n)H_(a)F_(b), C₆H_(c)F_(d), and OC₆H_(c)F_(d).

In one embodiment, in Formula II, both of R² together are a biarylenegroup, which may be further substituted. In one embodiment, thebiarylene group is selected from biphenylene and bipyridylene. Thesubstituent can be selected from F, Cl, Br, hydroxyl, carboxyl, cabonyl,silyl, siloxyl, alkyl, heteroalkyl, alkenyl, alkynyl, aryl, heteroaryl,alkylenearyl, alkenylaryl, alkynylaryl, alkyleneheteroaryl,alkenylheteroaryl, alkynylheteroaryl, C_(n)H_(a)F_(b), OC_(n)H_(a)F_(b),C₆H_(c)F_(d), and OC₆H_(c)F_(d).

In one embodiment, in Formula II, x is 0.

In one embodiment, in Formula II, R³ is selected from aryl, heteroaryl,alkyl, and heteroalkyl. In one embodiment, in Formula II, R³ is selectedfrom phenyl and substituted phenyl. In one embodiment, in Formula II, R³is selected from alkyl and heteroalkyl having from 1 through 12 carbonatoms, which may be further substituted.

In one embodiment, in Formula III, R¹ is selected from phenylalkenyl andphenylakynyl groups, which may be further substituted.

In one embodiment, in Formula III, R¹ is selected from alkylacetate andarylcarbonyl groups, which may be further substituted.

In one embodiment, in Formula III, R¹ is selected from alkyl groupshaving 1 through 12 carbon atoms.

In one embodiment in Formula III, R² is H.

In one embodiment in Formula III, R³ is selected from aryl, heteroaryl,alkyl, and heteroalkyl. In one embodiment, in Formula III, R³ isselected from phenyl and substituted phenyl. In one embodiment, inFormula III, R³ is selected from alkyl and heteroalkyl having from 1through 12 carbon atoms, which may be further substituted.

Specific examples of linked compounds having Formula II are given inFIG. 6, Formulae II(a) through II(l).

Electronic Device

The present invention also relates to an electronic device comprising atleast one of the charge transport compositions of the inventionpositioned between a photoactive layer and one electrode. A typicaldevice structure is shown in FIG. 8. The device 100 has an anode layer110 and a cathode layer 160. Adjacent to the anode is a layer 120comprising hole transport material. Adjacent to the cathode is a layer140 comprising an electron transport and/or anti-quenching material(“ET/AQ”). Between the hole transport layer and the electron transportand/or anti-quenching layer is the photoactive layer 130. As an option,devices frequently use another electron transport layer 150, next to thecathode. Layers 120, 130, 140, and 150 are individually and collectivelyreferred to as the active layers.

Depending upon the application of the device 100, the photoactive layer130 can be a light-emitting layer that is activated by an appliedvoltage (such as in a light-emitting diode or light-emittingelectrochemical cell), a layer of material that responds to radiantenergy and generates a signal with or without an applied bias voltage(such as in a photodetector). Examples of photodetectors includephotoconductive cells, photoresistors, photoswitches, phototransistors,and phototubes, and photovoltaic cells, as these terms are describe inMarkus, John, Electronics and Nucleonics Dictionary, 470 and 476(McGraw-Hill, Inc. 1966).

The quinoxaline derivative compounds of the invention are particularlyuseful as the electron transport and/or anti-quenching composition inlayer 140, or as electron transport composition in layer 150. Forexample, in one embodiment, the quinoxaline derivative compounds of theinvention may be used as the electron transport and/or anti-quenchinglayer in light emitting diode.

It is also to be understood that the ET/AQ material has to be chemicallycompatible with the photoactive material used. For example, the ET/AQmaterial has to form a smooth film when deposited on the photoactivematerial layer. If aggregation occurs, the performance of the devicewill deteriorate.

The other layers in the device can be made of any materials which areknown to be useful in such layers. The anode 110, is an electrode thatis particularly efficient for injecting positive charge carriers. It canbe made of, for example materials containing a metal, mixed metal,alloy, metal oxide or mixed-metal oxide, or it can be a conductingpolymer, and mixtures thereof. Suitable metals include the Group 11metals, the metals in Groups 4, 5, and 6, and the Group 8-10 transitionmetals. If the anode is to be light-transmitting, mixed-metal oxides ofGroups 12, 13 and 14 metals, such as indium-tin-oxide, are generallyused. The anode 110 may also comprise an organic material such aspolyaniline as described in “Flexible light-emitting diodes made fromsoluble conducting polymer,” Nature vol. 357, pp 477-479 (11 Jun. 1992).At least one of the anode and cathode should be at least partiallytransparent to allow the generated light to be observed.

Examples of hole transport materials which may be used for layer 120have been summarized, for example, in Kirk-Othmer Encyclopedia ofChemical Technology, Fourth Edition, Vol. 18, p. 837-860, 1996, by Y.Wang. Both hole transporting molecules and polymers can be used.Commonly used hole transporting molecules are:N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine(TPD), 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC),N,N′-bis(4-methylphenyl)-N,N′-bis(4-ethylphenyl)-[1,1′-(3,3′-dimethyl)biphenyl]-4,4′-diamine(ETPD), tetrakis-(3-methylphenyl)-N,N,N′,N′-2,5-phenylenediamine (PDA),a-phenyl-4-N,N-diphenylaminostyrene (TPS), p-(diethylamino)benzaldehydediphenylhydrazone (DEH), triphenylamine (TPA),bis[4-(N,N-diethylamino)-2-methylphenyl](4-methylphenyl)methane (MPMP),1-phenyl-3-[p-(diethylamino)styryl]-5-[p-(diethylamino)phenyl]pyrazoline(PPR or DEASP), 1,2-trans-bis(1H-carbazol-9-yl)cyclobutane (DCZB),N,N,N′,N′-tetrakis(4-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine (TTB),and porphyrinic compounds, such as copper phthalocyanine. Commonly usedhole transporting polymers are polyvinylcarbazole,(phenylmethyl)polysilane, and polyaniline and mixtures thereof. It isalso possible to obtain hole transporting polymers by doping holetransporting molecules such as those mentioned above into polymers suchas polystyrene and polycarbonate.

Examples of the photoactive layer 130 include all knownelectroluminescent materials. Organometallic electroluminescentcompounds are preferred. The most preferred compounds includecyclometalated iridium and platinum electroluminescent compounds andmixtures thereof. Complexes of Iridium with phenylpyridine,phenylquinoline, or phenylpyrimidine ligands have been disclosed aselectroluminescent compounds in Petrov et al., Published PCT ApplicationWO 02/02714. Other organometallic complexes have been described in, forexample, published applications US 2001/0019782, EP 1191612, WO02/15645, and EP 1191614. Electroluminescent devices with an activelayer of polyvinyl carbazole (PVK) doped with metallic complexes ofiridium have been described by Burrows and Thompson in published PCTapplications WO 00/70655 and WO 01/41512. Electroluminescent emissivelayers comprising a charge carrying host material and a phosphorescentplatinum complex have been described by Thompson et al., in U.S. Pat.No. 6,303,238, Bradley et al., in Synth. Met. (2001), 116 (1-3),379-383, and Campbell et al., in Phys. Rev. B, Vol. 65 085210 as havebeen Examples of a few suitable iridium complexes are given in FIG. 7,as Formulae VI(a) through VI(e). Analogous tetradentate platinumcomplexes can also be used. These electroluminescent complexes can beused alone, or doped into charge-carrying hosts, as noted above. Thequinoxaline materials of the present invention may also be used as suchcharge-carrying hosts in the emissive layer.

The cathode 160, is an electrode that is particularly efficient forinjecting electrons or negative charge carriers. The cathode can be anymetal or nonmetal having a lower work function than the anode. Materialsfor the cathode can be selected from alkali metals of Group 1 (e.g., Li,Cs), the Group 2 (alkaline earth) metals, the Group 12 metals, includingthe rare earth elements and lanthanides, and the actinides. Materialssuch as aluminum, indium, calcium, barium, samarium and magnesium, aswell as combinations, can be used. Li-containing organometalliccompounds, LiF, and Li₂O can also be deposited between the organic layerand the cathode layer to lower the operating voltage.

It is known to have other layers in organic electronic devices. Forexample, there can be a layer (not shown) between the anode 110 and holetransport layer 120 to facilitate positive charge transport and/orband-gap matching of the layers, or to function as a protective layer.Layers that are known in the art can be used. In addition, any of theabove-described layers can be made of two or more layers. Alternatively,some or all of anode layer 110, the hole transport layer 120, theelectron transport layers 140 and 150, and cathode layer 160, may besurface treated to increase charge carrier transport efficiency. Thechoice of materials for each of the component layers is preferablydetermined by balancing the goals of providing a device with high deviceefficiency with device operational lifetime.

It is understood that each functional layer may be made up of more thanone layer.

The device can be prepared by a variety of techniques, includingsequentially vapor depositing the individual layers on a suitablesubstrate. Substrates such as glass and polymeric films can be used.Conventional vapor deposition techniques can be used, such as thermalevaporation, chemical vapor deposition, and the like. Alternatively, theorganic layers can be applied from solutions or dispersions in suitablesolvents, using any conventional coating or printing technique,including but not limited to spin-coating, dip-coating, roll-to-rolltechniques, ink-jet printing, screen printing and gravure printing. Ingeneral, the different layers will have the following range ofthicknesses: anode 110, 500-5000 Å, preferably 1000-2000 Å; holetransport layer 120, 50-2000 Å, preferably 200-1000 Å; photoactive layer130, 10-2000 Å, preferably 100-1000 Å; electron transport layer 140 and150, 50-2000 Å, preferably 100-1000 Å; cathode 160, 200-10000 Å,preferably 300-5000 Å. The location of the electron-hole recombinationzone in the device, and thus the emission spectrum of the device, can beaffected by the relative thickness of each layer. Thus the thickness ofthe electron-transport layer should be chosen so that the electron-holerecombination zone is in the light-emitting layer. The desired ratio oflayer thicknesses will depend on the exact nature of the materials used.

The quinoxaline derivative compounds of the invention may be useful inapplications other than OLEDs. For example, these compositions may beused in photovoltaic devices for solar energy conversion. They may alsobe used in field effect transistor for smart card and thin filmtransistor (TFT) display driver applications.

EXAMPLES

The following examples illustrate certain features and advantages of thepresent invention. They are intended to be illustrative of theinvention, but not limiting. All percentages are by weight, unlessotherwise indicated.

Examples 1-16

These examples illustrate the preparation of quinoxaline derivativeET/AQ compositions.

Example 1

This example illustrates the preparation of Compound I(n) in FIG. 4.

An oven-dried resealable Schlenk flask was charged with2,3-(bi-4-fluorophenyl)-6-bromoquinoxaline (2.00 g, 5.00 mmol),para-tert-butylstyrene (1.02 g, 6.40 mmol), Na₂CO₃ (0.68 g, 6.40 mmol),trans-di(μ-acetato)bis[o-(di-o-tolyl-phosphino)benzyl]dipalladium (II)(0.020 g, 0.02 mmol) and 2,6-di-tert-butyl-p-cresol (0.552 g, 2.50 mmol)and N,N-dimethylacetamide (12 mL). The Schlenk flask was sealed with aTeflon valve and the reaction mixture was heated at 130° C. for 21 h.The resulting mixture was cooled to room temperature, diluted in Et₂O(230 mL) and filtered through a pad of silica. The filtrate was washedwith water (2×100 mL) and brine (1×50 mL). The organic layer was driedand concentrated to give a crude product which was then purified byflash chromatography to afford the pure product as a light-yellow solidin 72% (1.71 g) yield. ¹⁹F NMR (376.8 Hz, CD₂Cl₂): δ −113.48 and−113.58.

Example 2

This example illustrates the preparation of Compound I(o) in FIG. 4.

An oven-dried resealable Schlenk flask was charged with4-fluorophenylacetylene (0.334 g, 2.78 mmol),2,3-(bi-4-fluorophenyl)-6-bromoquinoxaline (1 g, 2.53 mmol), Pd₂(dba)₃(0.046 g, 0.05 mmol), triphenylphosphine (0.066 g, 0.253 mmol), CuI(0.010 g, 0.05 mmol) and triethylamine (15 mL). The flask was thensealed and heated at 60° C. for 24 hours. The reaction mixture wasdiluted with CH₂Cl₂, washed with H₂O and brine, dried over MgSO₄,filtered and concentrated to afford an off-white solid. The crudeproduct was purified by repeated washes with hexanes (3×20 mL) to yield0.924 g (84% yield). ¹H NMR (CD₂Cl₂, 500 MHz) δ 8.37 (d, 1H, J=1.6),8.20-8.18 (d, 1H, 8.8), 7.98-7.95 (dd, 1H, J=8.3, 1.5), 7.74-7.70 (dd,1H, J=5.4, 3.6), 7.64-7.60 (m, 1H), 7.24-7.14 (m, 1H). ¹⁹F NMR (CD₂Cl₂,500 MHz) δ −111.14 (m, 1F), −113.1 (m, 2F).

Example 3

This example illustrates the preparation of Compound I(q) in FIG. 4.

A reactor was charged with Compound I(n) from Example 1 (1.70 g, 3.55mmol), ESCAT 140 Pd/C catalyst (0.056 g), and MeOH (45 mL). The reactionmixture was flushed with nitrogen, pressurized to 500 psig H2 and heatedup to 60 C for 8 h. The volatiles were removed under vacuum and theproduct was purified by flash chromatography (5% EtOAc/hexane, where“Et” represents ethyl and “OAc” represents acetate) to yield alight-yellow powder (0.220 g, 13%). ¹⁹F NMR (376.8 Hz, CD₂Cl₂): δ−111.14 and −114.60.

Example 4

This example illustrates the preparation of Compound I(b) in FIG. 4.

A mixture of 3,4-diaminotoluene (28.78 g, 0.236 mol) and benzil (45 g,0.214 mol) was refluxed in 738 mL chloroform with 2.16 mLtrifluoroacetic acid for 3 hours. The mixture was washed 3 times with10% HCl, brine, and dried over MgSO₄, filtered, and then filteredthrough a silica bed with vacuum. The resultant solution was evaporatedto dryness. Recrystallized 69 grams of crude product from 550 mLmethanol. Filtered solids were dried in a vacuum oven at 50° C. for 1hour to yield 55.56 g of dried solid. 78.8% yield

Example 5

This example illustrates the preparation of Compound I(e) in FIG. 4.

A mixture of 3,4-diaminotoluene (4.49 g, 0.037 mol) and4,4′-dimethoxybenzil (9.46 g, 0.035 mol) was refluxed in 125 mLchloroform with 0.35 mL trifluoroacetic acid for 6 hours. The mixturewas washed 2 times with water, dried over MgSO₄, and evaporated to ˜11g. The solid was dissolved in 1:1 ethyl acetate:chloroform for flashchromatography and eluted with ethyl acetate. Evaporated to 9.7 grams ofdark solid. 72% yield

Example 6

This example illustrates the preparation of Compound I(c) in FIG. 4.

A mixture of 3,4-diaminotoluene (0.603 g, 4.93 mmol) and1,10-phenanthroline-5,6-dione (0.945 g, 4.50 mmol) was refluxed in 602mL chloroform with 0.35 mL trifluoroacetic acid for 6 hours. The mixturewas filtered hot through a medium frit to yield 0.85 g of light yellowsolid after drying. Yield 63%

A second crop was obtained from mother liquor after cooling to yield anadditional 0.31 g.

Example 7

This example illustrates the preparation of Compound I(d) in FIG. 4.

A mixture of 3,4-diaminotoluene (5.36 g, 44 mmol) and phenanthrenequinone (8.33 g, 0.040 mol) was refluxed in 119 mL chloroform with 0.4mL trifluoroacetic acid for 6 hours. The mixture was filtered through amedium frit and recrystallized from 430 g of methyl ethyl ketone toyield 5.5 g fluffy wool-like, yellow product. 46% yield

Example 8

This example illustrates the preparation of Compound I(f) in FIG. 4.

A mixture of 3,4-diaminotoluene (5.36 g, 44 mmol) and 2,2′-Pyridil (8.49g, 40 mmol) was refluxed in 119 mL chloroform with 0.4 mLtrifluoroacetic acid for 4 hours. The reaction mixture was separated andwashed 4 times with 100 mL water, and evaporated to 10.4 g. Theresultant solid was dissolved in 1:1 ethyl acetate:chloroform for flashchromatography and eluted with ethyl acetate. Evaporated to yield 9.3 gof solid.

Example 9

This example illustrates the preparation of Compound I(g) in FIG. 4.

A mixture of methyl-3,4-diaminobenzoate (7.28 g, 44 mmol) and benzil(8.41 g, 40 mmol) was refluxed in 140 ml methylene chloride for 21hours. The reaction mixture was evaporated to dryness and then dissolvedin 520 mL methanol and 150 mL methylene chloride at reflux. The solutionwas then partially evaporated to selectively crystallize the desiredproduct

Example 10

This example illustrates the preparation of Compound I(k) in FIG. 4.

A mixture of Methyl-3,4-diaminobenzoate (6.37 g, 0.038 mol) and4,4′-dimethoxybenzil (9.46 g, 0.035 mol) was refluxed in 142 mLmethylene chloride with 3 drops trifluoroacetic acid for 5 hours. 10.7 gN-methylpyrrolidinone was added and reflux continued for 26 more hours.The mixture was washed 3 times with water, dried over MgSO₄, filteredand then precipitated the product be decanting the organic solution into550 g methanol. After standing overnight, the product was filtered anddried at 95° C. in vacuum to yield 10.39 g product.

Example 11

This example illustrates the preparation of Compound I(r) in FIG. 4.

A mixture of Methyl-3,4-diaminobenzoate (6.12 g, 0.037 mol) andphenanthrene quinone (7.08 g, 0.034 mol) was refluxed in 119 mLmethylene chloride. 100 g of N-methylpyrrolidinone was added and thechlorinated solvent was distilled out. The pot was warmed to 150° C.whereupon a clear solution was obtained and the reaction was tracked bygas chromatography. The product was precipitated by pouring into 410 gmethanol and the solid precipitate filtered off. The product wasrecrystallized from toluene then recrystallized again from a combinationof methyl ethyl ketone 1200 g, toluene 150 g, and tetrahydrofuran 1100g. Yield was 3.3 g of pearly golden wool-like material.

Example 12

This example illustrates the preparation of Compound I(l) in FIG. 4.

A mixture of 1,2-phenylenediamine (13.91 g, 0.129 mol) and4,4′-dibromobenzil (45 g, 0.116 mol) was refluxed in 558 mL chloroformwith 1.0 ml trifluoroacetic acid for 6 hours. The mixture was washed 3times with 10% HCl, and evaporated to ˜51 g. Recrystallized from 600 mLethyl acetate with 100 mL methanol at reflux. Large crystals formedovernight and were filtered and washed with methanol twice and dried to29.63 g with a 4.9 g second crop from the chilled mother liquor.

Example 13

This example illustrates the preparation of Compound I(h) in FIG. 4.

A mixture of 2,3-diaminotoluene (4.84 g, 0.040 mol) and benzil (7.56 g,0.036 mol) was refluxed in 112 mL methylene chloride for 19 hours. Themixture was washed 4 times with 12% HCl, and dried over MgSO₄ filteredand evaporated to ˜9.5 g of brown solid. The solid was dissolved into495 g methanol at reflux and then ˜300 g solvent was distilled out.Cooling with ice yielded nice crystals. Filtered and washed crystal cakewith methanol.

Example 14

This example illustrates the preparation of Compound I(i) in FIG. 4.

A mixture of 2,3-diaminotoluene (5.05 g, 0.041 mol) andphenanthrenequinone (7.84 g, 0.038 mol) were refluxed in 112 mlchloroform for 29 hours. The resultant solution was chromatographed downa silica column with chloroform eluant. Evaporated product from solventto yield about 10 g before vacuum oven drying. Material appearedcrystalline

Example 15

This example illustrates the preparation of Compound I(j) in FIG. 4.

A mixture of methyl-3,4-diaminobenzoate (7.28 g 0.044 mol) and2,2′-pyridil (8.48 g, 0.040 mol) was refluxed in 140 mL methylenechloride for 7 hours. The solution was evaporated to 15.7 g and thesolid dissolved in 240 mL methylene chloride and 140 mL methanol atreflux. After addition of 280 mL methanol and evaporation of ˜150 mL ofthe solvent the solution was left to stand overnight. The resultingsolid was collected and dried to 9.8 g. Took 7.7 g material anddissolved in 203 g methanol with 50 g methylene chloride. Distilledoff >50 mL of solvent. Crystals formed overnight. Filtered and dried invacuum oven.

Example 16

This example illustrates the preparation of Compound I(t) in FIG. 4.

An oven-dried resealable Schlenk flask was charged with2,3-(bi-4-fluorophenyl)-6-bromoquinoxaline (1.23 g, 3.08 mmol),1,3-divinyltetramethyldisiloxane (3.40 mL, 14.8 mmol), KOAc (0.440 g,4.48 mmol), Pd(OAc)₂ (0.012 g, 0.06 mmol), P(o-Tol)₃ (0.06 g, 0.20mmol), NEt₃ (0.300 mL), DMF (˜2 mL) and water (0.45 mL). The Schlenkflask was sealed with a Teflon valve and the reaction mixture was heatedat 95° C. for 48 h. The resulting mixture was cooled to roomtemperature, diluted in water (15 mL) and the product was extracted withCH₂Cl₂ (15 mL). The organic layer was dried and concentrated to give acrude product, which was purified by chromatography (3% EtOAc/hexane) asa light-yellow solid (0.478 g, 31% yield). ¹⁹F NMR (376.8 Hz, CD₂Cl₂): δ−113.45 (br m).

Examples 17-19

These examples illustrate the preparation of charge transportcompositions having more than one quinoxaline group.

Example 17

This example illustrates the preparation of Compound II(d) in FIG. 6.

A 3-necked 500 mL round bottomed flask fitted with a nitrogen inlet anda condensor was charged with 1,4-phenylenebisboronic acid (2 g, 12.1mmol), 2,3-(bi-4-fluorophenyl)-6-bromoquinoxaline (9.54 g, 24.1 mmol),Pd(PPh₃)₄ (2.78 g, 2.41 mmol), potassium carbonate (6.67 g, 48.3 mmol),DME (150 mL) and H₂O (150 mL). The reaction mixture was refluxed for 24h, after which it was diluted with H₂O and CH₂Cl₂. The organic layercontained a precipitate, which was isolated by filtration and washedwith CH₂Cl₂ to yield 2.75 g (32% yield) of an off-white powder. ¹H NMR(CD₂Cl₂, 500 MHz) δ 8.56-8.55 (m, 1H), 8.35-8.33 (d, 1H), 8.29 (m, 1H),8.12 (s, 1H), 7.68-7.64 (m, 1H), 7.29-7.16 (m, 1H). ¹⁹F NMR (CD₂Cl₂, 500MHz) δ −113.35 (m, 2F).

Example 18

This example illustrates the preparation of Compound II(j) in FIG. 6.

A mixture of 1,4-bisbenzil (1 g, 2.92 mmol) and4,5-dimethyl-1,2-phenylenediamine (0.769 g, 5.84 mmol) in chloroform (20mL) was refluxed for 15 hrs under an atmosphere of nitrogen. Hexanes wasadded to reaction mixture, precipitating out a bright yellow precipitatewhich was isolated by filtration and washed with hexanes to yield theproduct as a bright-yellow powder (1.32 g, 83% yield). ¹H NMR (CD₂Cl₂,500 MHz) δ 7.89-7.88 (d, 1H, J=7.1 Hz), 7.50-7.48 (dd, 1H, J=1.5 Hz, 7.7Hz), 7.45 (s, 1H), 7.35-7.31 (m, 1H), 2.53 (s, 1H).

Example 19

This example illustrates the preparation of Compound II(a) in FIG. 6.

A mixture of 3,3-diaminobenzidine (0.4580 g, 2.14 mmol) and1,10-phenanthroline-5,6-dione (0.9458 g, 4.5 mmol) was heated at 85° C.in 10 g N-methylpyrrolidinone with 0.045 ml trifluoroacetic acid for 23hours. At ambient temperature chloroform was charged to the pot and thecontents were filtered through a fine frit and washed with acetone, anddiethylether then dried at 90° C. and vacuum.

Example 20

This example illustrates the preparation of Compound I(m) in FIG. 4.

The synthesis of this compound was carried out following the syntheticmethod used for the preparation of I(o) to give the desired product in58% yield. ¹H NMR (CD₂Cl₂, 500 MHz) δ 8.38 (d, 1H, J=1.8 Hz), 8.20-8.18(d, 1H, 8.4 Hz), 7.99-7.97 (dd, 1H, J=1.8 Hz, 8.7 Hz), 7.73-7.71 (m,1H), 7.64-7.61 (m, 1H), 7.52-7.50 (m, 1H), 7.19-7.14 (m, 1H). ¹⁹F NMR(CD₂Cl₂, 500 MHz) δ −113.14 (m, 2F).

Example 21

This example illustrates the preparation of Compound II(f) in FIG. 6.

The synthesis of this compound was carried out following the syntheticmethod used for the preparation of II(e) to give the desired product in13% yield. ¹H NMR (CD₂Cl₂, 500 MHz) δ 8.42-8.41 (d, 1H, J=1.9),8.20-8.18 (d, 1H, J=8.5), 8.13-8.11 (dd, 1H, J=9.1 Hz, 2.0 Hz), 8.00 (s,1H), 7.54-7.51 (dd, 1H, J=8.7 Hz, 3.1 Hz), 6.9-6.9 (q, 1H), 5.48 (s,1H).

Example 22

This example illustrates the preparation of Compound II(c) in FIG. 6.

The synthesis of this compound was carried out following the syntheticmethod used for the preparation of II(e) to give the desired product in10% yield. ¹H NMR (CD₂Cl₂, 500 MHz) δ 8.62-8.61 (d, 1H, J=1.5),8.44-8.41 (m, 1H), 8.41-8.39 (d, 1H, J=9.5 Hz), 8.34-8.31 (dd, 1H, J=8.3Hz, 1.6 Hz), 8.14 (m, 1H), 8.12-8.11 (m, 1H), 7.98-7.94 (m, 1H),7.38-7.34 (m, 1H).

Example 23

This example illustrates the preparation of Compound II(j) in FIG. 6.

The synthesis of this compound was carried out following the syntheticmethod used for the preparation of II(j) to give the desired product in66% yield. ¹H NMR (CD₂Cl₂, 500 MHz) δ 8.09-8.06 (t, 1H, J=7.4 Hz),7.98-7.96 (d, 1H, J=7.2 Hz), 7.69-7.67 (d, 1H, 8.9), 7.59-7.51 (m, 1H),7.43-7.40 (m, 1H), 2.67 (s, 1H).

Example 24

This example illustrates the preparation of Compound II(k) in FIG. 6.

The synthesis of this compound was carried out following the syntheticmethod used for the preparation of II(j) to give the desired product in65% yield. ¹H NMR (CD₂Cl₂, 500 MHz) δ 8.29-8.24 (m, 1H), 8.07-8.01 (m,1H), 7.90-7.86 (m, 1H), 7.80-7.78 (m, 0.6H), 7.72-7.66 (m, 1H),7.64-7.59 (m, 1H), 7.51-7.44 (m, 1H). ¹⁹F NMR (CD₂Cl₂, 500 MHz) δ −108.4(m, 2F), −108.9 (m, 3F), −109.2 (m, 8F), −109.4 (m, 8F).

Example 25

This example illustrates the preparation of Compound II(l) in FIG. 6.

The synthesis of this compound was carried out using the syntheticscheme shown below.

Compound II(ma) was obtained using the synthetic method used for I(o) toproduce the expected product in 65% yield. ¹H NMR (CD₂Cl₂, 500 MHz) δ7.64-7.60 (m, 1H), 7.27 (s, 1H), 7.20-7.16 (t, 1H, J=8.9 Hz). ¹⁹F NMR(CD₂Cl₂, 500 MHz) δ −111.10 (m, 2F). Under nitrogen, a three-neckedround bottomed flask fitted with a condensor was charged with II(ma)(2.00 g, 6.25 mmol, 0.1 equiv.), Adogen 464 (0.125 g), potassiumpermanganate (4.9 g, 31.25 mmol, 5.00 equiv.), sodium bicarbonate (1.05g, 12.5 mmol, 2.0 equiv.), H₂O (80 mL) and CH₂Cl₂ (50 mL). The mixturewas allowed to reflux for 36 hours. After cooling to room temperature,9.3 g sodium bicarbonate and 4 mL HCl were slowly added to the reactionmixture to neutralize and remove any excess oxidizing agents. Thereaction mixture was then diluted with dichloromethane and H₂O, thelayers separated and the organic portion washed with H₂O, brine anddried over MgSO₄. The product was isolated by evaporating the solventand then was recrystallized from ethanol to give 0.6 g (25% yield) ofII(mb) as yellow needle-like crystals. ¹H NMR (CD₂Cl₂, 500 MHz): δ8.25-8.21 (dd, 1H, J=8.9 Hz, 5.6 Hz), 7.98 (s, 1H), 7.36-7.32 (t, 1H,J=8.70 Hz). ¹⁹F NMR (CD₂Cl₂, 500 MHz): δ −101.8 (m, 2F). The synthesisof compound II(m) was carried out following the procedure used for thepreparation of II(k) to give the desired product in 20% yield. ¹H NMR(CD₂Cl₂, 500 MHz) δ 8.25-8.21 (m, 1H), 8.19-8.15 (m, 1H), 7.85-7.78 (m,1H), 7.73-7.64 (m, 1H), 7.29-7.25 (t, 1H), 6.69-6.66 (m, 1H). ¹⁹F NMR(CD₂Cl₂ 500 MHz) δ −108.7, −108.8 (m, 2F), −112.4 (m, 1F), −112.6 (m,1F).

The properties of the electron transport and/or anti-quenchingcompositions are summarized in Table 1 below.

TABLE 1 Properties Absorption Absorption LUMO vs onset (nm), maximumE_(1/2) vs SCE vacuum (eV), Compounds E1-E5 (nm) (volt), E1 Compound 375345 −1.5  −3.33 I(a) Compound 378 339 −1.6  −3.24 I(b) Compound 400 385−1.17 −3.67 I(c) Compound 410 397 −1.3  −3.54 I(d) Compound 390 352−1.29 −3.55 I(g) Compound — — — —what is the II(a) purpose of this line?Compound 405 369 −1.66 −3.18 I(e) Compound 378 339 −1.53 −3.31 I(f)Compound 420 382 −1.35 −3.49 I(o) Compound 407 394 −1.28 −3.56 I(l)Compound 385 343 −1.59 −3.25 I(k) Compound 417 401 −1.03 −3.81 I(w)Compound 380 347 −1.49 −3.35 I(p) Compound 380 342 −1.22 −3.62 I(x)Comp. A 368 310 −1.85 −2.99 DDPA Comp. B 366 316 −1.95 −2.89 DPA

Example 27

This example illustrates the preparation of an iridiumelectroluminescent complex, shown as Formula V(a) in FIG. 7.

Phenylpyridine ligand, 2-(4-fluorophenyl)-5-trifluoromethylpyridine

The general procedure used was described in O. Lohse, P. Thevenin, E.Waldvogel Synlett, 1999, 45-48. A mixture of 200 ml of degassed water,20 g of potassium carbonate, 150 ml of 1,2-dimethoxyethane, 0.5 g ofPd(PPh₃)₄, 0.05 mol of 2-chloro-5-trifluoromethylpyridine and 0.05 molof 4-fluorophenylboronic acid was refluxed (80-90° C.) for 16-30 h. Theresulting reaction mixture was diluted with 300 ml of water andextracted with CH₂Cl₂ (2×100 ml). The combined organic layers were driedover MgSO₄, and the solvent removed by vacuum. The liquid products werepurified by fractional vacuum distillation. The solid materials wererecrystallized from hexane. The typical purity of isolated materials was>98%.

Iridium Complex:

A mixture of IrCl₃.nH₂O (54% Ir; 508 mg),2-(4-fluorophenyl)-5-trifluoromethylpyridine, from above (2.20 g),AgOCOCF₃ (1.01 g), and water (1 mL) was vigorously stirred under a flowof N₂ as the temperature was slowly (30 min) brought up to 185° C. (oilbath). After 2 hours at 185-190° C. the mixture solidified. The mixturewas cooled down to room temperature. The solids were extracted withdichloromethane until the extracts decolorized. The combineddichloromethane solutions were filtered through a short silica columnand evaporated. After methanol (50 mL) was added to the residue theflask was kept at −10° C. overnight. The yellow precipitate of thetris-cyclometalated complex, compound V(a) in FIG. 7A, was separated,washed with methanol, and dried under vacuum. Yield: 1.07 g (82%). X-Rayquality crystals of the complex were obtained by slowly cooling its warmsolution in 1,2-dichloroethane.

Example 28

This example illustrates the formation of OLEDs using the chargetransport compositions of the invention.

Thin film OLED devices including a hole transport layer (HT layer),electroluminescent layer (EL layer) and at least one electron transportand/or anti-quenching layer (ET/AQ layer) were fabricated by the thermalevaporation technique. An Edward Auto 306 evaporator with oil diffusionpump was used. The base vacuum for all of the thin film deposition wasin the range of 10⁻⁶ torr. The deposition chamber was capable ofdepositing five different films without the need to break up the vacuum.

Patterned indium tin oxide (ITO) coated glass substrates from Thin FilmDevices, Inc was used. These ITO's are based on Corning 1737 glasscoated with 1400 Å ITO coating, with sheet resistance of 30 ohms/squareand 80% light transmission. The patterned ITO substrates were thencleaned ultrasonically in aqueous detergent solution. The substrateswere then rinsed with distilled water, followed by isopropanol, and thendegreased in toluene vapor for ˜3 hours.

The cleaned, patterned ITO substrate was then loaded into the vacuumchamber and the chamber was pumped down to 10⁻⁶ torr. The substrate wasthen further cleaned using an oxygen plasma for about 5-10 minutes.After cleaning, multiple layers of thin films were then depositedsequentially onto the substrate by thermal evaporation. Finally,patterned metal electrodes of Al or LiF and Al were deposited through amask. The thickness of the film was measured during deposition using aquartz crystal monitor (Sycon STC-200). All film thickness reported inthe Examples are nominal, calculated assuming the density of thematerial deposited to be one. The completed OLED device was then takenout of the vacuum chamber and characterized immediately withoutencapsulation.

Table 2 summarizes the devices made with the quinoxaline derivativeET/AQ compositions of the invention. In all cases the anode was ITO, asdiscussed above, the hole transport layer was MPMP, and the emittinglayer was the iridium complex from Example 27, having the thicknessesindicated. When present, electron transport layer 150 wastris(8-hydroxyquinolato)aluminum(III), Alq, having the thicknessesgiven. The cathode was a layer of Al or a dual layer of LiF/Al, with thethicknesses given.

TABLE 2 Devices Sample HT (Å) EL, Å ET/AQ, Å ET, Å Cathode, ÅComparative A 507 407 Comp. A Al 721 408 Comparative B 507 405 Comp. BAl 732 407 3-1 545 403 I(a) Alq 430 Al 737 430 3-2 508 625 I(b) Al 732425 3-3 509 413 I(c) Al 750 416 3-4 578 411 I(d) Al 711 381 3-5 527 418I(e) Al 1027 418 3-6 535 415 I(f) Al 1039 459 3-7 549 425 I(g) Al 1023423 3-8 510 445 II(a) Al 710 415 3-9 502 403 I(f) Alq 303 LiF 5 106 Al470 3-10 502 402 I(d) Alq 303 LiF 5 102 Al 497 3-11 501 402 I(c) Alq 302LiF 5 103 Al 111 3-12 513 409 I(h) Al 718 414 3-13 514 416 I(i) Al 718408 3-14 515 500 I(i) Al 729 410 3-15 504 488 I(j) Al 721 402 3-16 505412 I(k) Al 727 439 3-17 516 409 I(l) Al 733 432 3-18 302 403 II(c) Alq302 LiF 10 102 Al 452 3-19 304 402 II(d) Alq 302 LiF 10 101 Al 452 3-20305 404 II(e) Alq 303 LiF 10 102 Al 454 3-21 301 402 II(f) Alq 305 LiF10 105 Al 451 3-22 303 406 I(m) Alq 302 LiF 10 103 Al 453 3-23 303 405II(g) Alq 305 LiF 10 102 Al 453 3-24 304 402 I(n) Alq 303 LiF 10 101 Al453 3-25 303 410 II(h) Alq 305 LiF 10 102 Al 453 3-26 306 404 I(o) Alq302 LiF 10 103 Al 453 3-27 305 404 II(i) Alq 305 LiF 10 192 Al 453 3-28303 402 I(p) Alq 304 LiF 10 102 Al 456 3-29 303 403 II(j) Alq 303 LiF 10103 Al 335 3-30 303 405 II(k) Alq 305 LiF 10 102 Al 284 3-31 303 405II(l) Alq 303 LiF 10 102 Al 232

The OLED samples were characterized by measuring their (1)current-voltage (I-V) curves, (2) electroluminescence radiance versusvoltage, and (3) electroluminescence spectra versus voltage. Theapparatus used, 200, is shown in FIG. 9. The I-V curves of an OLEDsample, 220, were measured with a Keithley Source-Measurement Unit Model237, 280. The electroluminescence radiance (in the unit of cd/m²) vs.voltage was measured with a Minolta LS-110 luminescence meter, 210,while the voltage was scanned using the Keithley SMU. Theelectroluminescence spectrum was obtained by collecting light using apair of lenses, 230, through an electronic shutter, 240, dispersedthrough a spectrograph, 250, and then measured with a diode arraydetector, 260. All three measurements were performed at the same timeand controlled by a computer, 270. The efficiency of the device atcertain voltage is determined by dividing the electroluminescenceradiance of the LED by the current density needed to run the device. Theunit is in cd/A.

The results for devices using the quinoxaline derivative ET/AQcompositions of the invention are given in Table 3 below:

TABLE 3 Electroluminescent Properties of Devices Efficiency at Peak PeakPeak Peak power Radiance, Radiance efficiency, efficiency Sample cd/m2cd/A cd/A lm/W Comp. F 3000 10 14 at 22 V Comp. G 4500 10 20 at 19 V3-1  2300 4 5.4 at 20 V 3-2  2700 10 at 27 V 3-3  4000 10-16 at 15 V3-4  90 4.4 at 22 V 3-5  200 1.1 at 22 V 3-6  2500 8.5 at 21 V 3-7  200013 at 22 V 3-8  290 1.8 at 16 V 3-9  7000 30 15 at 15 V 3-10 1000 14 at25 V 3-11 6500 26 at 15 V 3-12 1200 9.5 at 20 V 3-13 300 2.6 at 19 V3-14 220 2.6 at 26 V 3-15 180 8.5 at 25 V 3-16 1600 11 at 22 V 3-17 1001.2 at 22 V 3-18 4200-5800 16-20 at 15 V 3-19 4000-5000 17-20 at 15 V3-20 4800-5400 15-17 at 17 V 3-21 2300 10.5 at 20 V 3-22 4000 15-19 at17 V at 13 V 3-23 5000 17-22 at 17 V at 13 V 3-24 5600 22 at 17 V at 14V 3-25 1400 5.5 at 17 V at 13 V 3-26 8000 20 at 14 V at 11 V 3-27 700016 at 17 V at 14 V 3-28 6000 15-20 at 15 V at 14-11 V 3-29 6500 18 at 16V at 13 V 3-30 6500 19 at 15 V at 11 V 3-31 6000 14 at 16 V at 12 V

1. An electronic device comprising a photoactive layer and a secondlayer, wherein at least one layer comprises a quinoxaline derivativeselected from Formula II in FIG. 2 and Formula III in FIG. 3:

wherein: R¹ and R² are the same or different at each occurrence and areselected from H, F, Cl, Br, alkyl, heteroalkyl, alkenyl, alkynyl, aryl,heteroaryl, alkylenearyl, alkenylaryl, alkynylaryl, alkyleneheteroaryl,alkenylheteroaryl, alkynylheteroaryl, C_(n)H_(a)F_(b), OC_(n)H_(a)F_(b),C₆H_(c)F_(d), and OC₆H_(c)F_(d), or both of R² together may constitutean arylene or heteroarylene group; R³ is the same or different at eachoccurrence and is selected from a single bond and a group selected fromalkylene, heteroalkylene, arylene, heteroarylene, arylenealkylene, andheteroarylenealkylene; Q is selected from a single bond and amultivalent group; a, b, c, and d are 0 or an integer such thata+b=2n+1, and c+d=5; m is an integer equal to at least 2; n is aninteger; p is 0 or 1; and x is 0 or an integer from 1 through
 3. 2. Thedevice of claim 1, wherein the second layer comprises a quinoxalinederivative having Formula II in FIG. 2, and further wherein: m is aninteger from 2 through 10; n is an integer from 1 through 12; with theproviso that when Q is a single bond, p is
 0. 3. The device of claim 1,wherein the second layer comprises a quinoxaline derivative havingFormula II in FIG. 2, and further wherein: R¹ and R² are the same ordifferent at each occurrence and are selected from H, F, Cl, Br, alkyl,heteroalkyl, aryl, heteroaryl, alkylenearyl, alkenylaryl, alkynylaryl,alkyleneheteroaryl, alkenylheteroaryl, alkynylheteroaryl,C_(n)H_(a)F_(b), OC_(n)H_(a)F_(b), C₆H_(c)F_(d), and OC₆H_(c)F_(d), orboth of R² together may constitute an arylene or heteroarylene group; mis an integer from 2 through 10; n is an integer from 1 through 12; andp is
 0. 4. The device of claim 1, wherein R¹ is selected from phenyl andsubstituted phenyl groups.
 5. The device of claim 4, wherein R¹ isselected from substituted phenyl groups having at least one substituentselected from F, Cl, Br, alkyl groups, heteroalkyl groups, alkenylgroups, and alkynyl groups.
 6. The device of claim 1, wherein R¹ isselected from alkylacetate and arylcarbonyl groups.
 7. The device ofclaim 1, wherein R¹ is selected from alkyl groups having from 1 to 12carbon atoms.
 8. The device of claim 1, wherein R² is selected fromphenyl groups, substituted phenyl groups, pyridyl groups, andsubstituted pyridyl groups.
 9. The device of claim 1, wherein R²together form a biarylene group.
 10. The device of claim 9, wherein thebiarylene group is selected from biphenylene, substituted biphenylene,bipyridylene, and substituted bipyridylene.
 11. The device of claim 1,wherein R³ is selected from aryl, heteroaryl, alkyl, and heteroalkyl.12. The device of claim 1, wherein R³ is selected from phenyl andsubstituted phenyl.
 13. The device of claim 1, wherein R³ is selectedfrom alkyl and heteroalkyl having from 1 to 12 carbon atoms.
 14. Thedevice of claim 1 wherein Q is selected from a hydrocarbon group with atleast two points of attachment, selected from an aliphatic group, aheteroaliphatic group, an aromatic group, and a heteroaromatic group.15. The device of claim 1 wherein Q is selected from alkylene groups,hetereoalkylene groups, alkenylene groups, heteroalkenylene groups,alkynylene groups, and heteroalkynylene groups.
 16. The device of claim1 wherein Q is selected from single-ring aromatic groups, multiple-ringaromatic groups, fused-ring aromatic groups, single-ring heteroaromaticgroups, multiple-ring aromatic groups, fused-ring aromatic groups,arylamines, silanes and siloxanes.
 17. The device of claim 1, wherein Qis selected from Formulae IV(a)-IV(h):


18. The device of claim 1, wherein the quinoxaline derivative isselected from Formulae II (a) through II (m) in Figure:


19. The device of claim 18, wherein the quinoxaline derivative isselected from Formulae II(a), II(h), II(l) and II(m).
 20. An electronicdevice of claim 18, wherein the device is a light-emitting diode,light-emitting electrochemical cell, or a photodetector.